Microwave-Assisted Solvothermal Synthesis of Cupric Oxide Nanostructures for High-Performance Supercapacitor

Abstract

Enhancing the performance and stability of the low-cost materials for electrochemical energy storage device is an important aspect. Herein, we report microwave-assisted solvothermal synthesis of three-dimensional (3D) spherical CuO structures composed of either one-dimensional (rod-like) or two-dimensional (2D) flake-like building blocks by varying the reaction medium, i.e., water and ethylene glycol (EG). A higher EG in the reaction medium facilitates formation of the flake-like structures. A specific surface area of 168.47 m2 g–1 is achieved with the 3D flower-like CuO, synthesized using copper acetate precursor in 1:3 water/EG solvent ratio. The same sample delivers a specific capacitance of 612 F g–1 at an applied current density of 1 A g–1 and shows high stability with capacity retention of 98% after 4000 galvanostatic charge–discharge cycles. The high specific capacitance of flower-shaped CuO architecture is attributed to large surface area and availability of sufficient pores for ions diffusion. Furthermore, two-electrode asymmetric supercapacitor device is fabricated using the 3D flower-shaped CuO as positive electrode and activated carbon as negative electrode, which shows an energy density of 27.27 Wh kg–1 at a power density of 800 W kg–1. This underlines the potential of inexpensive CuO architecture as an active material for energy storage devices.